Field of the Invention
The present invention relates to a technique for improving performance of detecting a movement amount of an object based on a captured image.
Description of the Related Art
Panning is a method of photographing at a slower shutter speed than a normal shutter speed while following a moving object (object). Since it is possible to acquire an image with a moving background and a still object by panning, photos having a high sense of speed can be photographed. However, since long-time photographing is performed, it is difficult to match a velocity of an object and a shake velocity of a camera during an exposure period. This is one of photographing techniques requiring mastery of skills.
As a photography assist technique to suitably perform panning, there is a method of detecting a difference between a velocity of an object and a shake velocity of a camera and correcting an amount of blurring corresponding to the difference using an image shake correction function. An angular velocity sensor in a camera immediately before photography detects an angular velocity for the panning of the camera following the object, and an amount of movement of an image of a main object on an imaging surface is detected. It is possible to calculate an angular velocity of an object from the detected panning angular velocity and an amount of movement of an object image on an image surface. During the exposure, shake correction processing is executed according to an amount of difference between the calculated angular velocity of a main object and an angular velocity sensor output in the camera. It is possible to suppress blurring of the main object which is a panning target by a difference in panning velocity between the main object and the camera and correction on an amount of camera shake.
An important issue in the method is to more accurately determine an angular velocity of an object, that is, an angular velocity at which a photographer needs to pan a camera in accordance with the object to stop an image of the object at which the photographer aims. That is, when an error occurs in the angular velocity, the error may occur in correction by an image shake correction function. There is a possibility of errors appearing in an image as leftover blurring. In order to accurately determine an angular velocity of a main object, an amount of movement on an image surface needs to be detected and a motion vector needs to be detected by comparing an image of a current frame and an image of a next frame. In this case, a motion vector for each divided region (block) in an image may not be able to be accurately detected because it exceeds a search range set in advance when the motion vector is detected. In Japanese Patent Laid-Open No. 2014-60654, it is disclosed that an image is reduced in size and the number of pixels in the search region is decreased to substantially expand the search range.
However, the prior art disclosed in Japanese Patent Laid-Open No. 2014-60654 has a possibility of an amount of movement of an object being unable to be accurately detected if an image of an object becomes unclear due to a reduction in size of an image. When there are few chances to take photographs while panning, it is desirable to reduce the possibility of failure as much as possible.